PYTHON

Circumference of circle

import math
C = 2 * math.pi * r

circumference of a circle

C = 2*pi*R

circumference of circle

C = Pi * r * 2 (r stands for radius)

Or you could do this:
C = Pi * d (d stands for diameter)

area and circumference of a circle

#include <stdio.h>
#define PI 3.142
int main(){
    float r, C, A;
    printf("What is the radius: 
");
    scanf("%f", &r);
    C = 2 * PI * r;
    A = PI * r * r;
    printf("
Cincumference is and %f Area is %f
", C, A);
}

circumference circle

from math import pi
Circumference = pi * diameter  
Circumference = pi * 2 * radius